1. Field of the Invention
The invention relates to a slide rail for tightening a transmission connecting two drive wheels.
2. Description of the Prior Art
A slide rail of this type has already been disclosed by EP 0113685. It is adjusted, via a lever system and a spring, in the direction of the chain. It thus automatically tightens the unloaded section of the chain running between two drive wheels. The slide rail guides the chain on a relatively long guide surface and is therefore curved in conformity with the unstretched course of the chain. In addition, with steady elongation of the chain, the slide rail must ensure secure guidance during the entire period of operation. Owing to unavoidable periods of inertia, due to shock loads or uneven travel, from time to time the load-free section of the chain becomes somewhat elongated, whereby the slide rail yields to the force of the spring and at least equalizes the sectional variations in length occurring between the drive wheels. However, especially with very strong accelerations in the motional behavior of the slide rail, the latter may briefly detach from the chain and as a possible result fail to resume its task as a tightening element in timely enough fashion. To avoid these disadvantages, attempts have been made to influence the motion of the slide rail by a hydraulic damping piston.
Hydraulic dampers, however, have the disadvantage that after a certain period of operation they exhibit an idle stroke, albeit a small one, due to losses from leakage. Under these conditions damping can no longer be expected. However, slight motions, due to vibrations, which occur in the chain-tightening devices result in increased wear and especially in severe noise.